Pamukkale is on the UNESCO World Heritage list with its white travertines and ancient city of Hierapolis. Nature and history combined.
Walk on the travertines barefoot; go in the morning or late afternoon as they get very hot. Don't miss the Hierapolis theatre and necropolis. You can swim in the antique pool.
Nearby Denizli city centre and Kaklık Cave are also worth a visit. Stay in Pamukkale village or Denizli.